The invention concerns the field of spinning mill technology and relates to a method and device of piecing a yarn on a spinning frame. The method according to the invention serves for piecing the yarn which is formed of a staple fiber material in a spinning frame and/or in a spinning position of an air spinning frame, for example, after a can change, after a bobbin change, after a yarn breakage or after another spinning disturbance. The method can likewise serve for the starting of spinning, i.e., for the restart of a spinning process. The invention also concerns a spinning position, being equipped for the execution of the method according to the invention.
Speaking of air spinning frames, a device is to be understood for the production of a spun yarn from a fiber strand comprising a fiber guiding channel with a fiber guiding surface for the guiding of the fibers of the fiber strand into an inlet port of a thread guiding channel. The device also includes a fluid device for the generation of a turbulence around an inlet port of the thread guiding channel and the measure according to the invention for the influence of the flow conditions within the spindle channel of a stationary spindle.
Air spinning frames for the spinning of staple fiber materials usually comprise a large number of spinning positions, whereby, in each spinning position, a yarn is spun from a supplied longitudinal fiber structure. Thereby, the longitudinal fiber structure is first being refined, i.e., the fiber amount per unit of length becomes reduced by way of drafting.
The refined fiber strand is then spun into a yarn by generating a twist in the yarn. The yarn is then withdrawn and wound up. For the refinement, the longitudinal fiber structure is drafted, for example, by means of a drafting unit or dissolved with the help of a dissolving roller. For the yarn formation by means of twist generation, an air spinning method is used, i.e., the yarn formation is achieved by air twist generation.
After an interruption of the air spinning process where the connection between the spun thread and the refined fiber strand (longitudinal fiber structure) to be spun is broken, this connection must again be repaired, not only, so that the produced yarn is without interruptions, but also, that the spinning process can be started again. For such a reconnection of yarn and longitudinal fiber structure, in particular with air spinning methods, the free yarn end resulting from the interruption is pulled out upstream against the normal yarn conveying direction through the twist generating point and then positioned there. Thereafter, the thread take-off and the air twist generation means are again put into operation and the free front end (beginning) of the refined longitudinal fiber structure is supplied to the air twist generation, in such a manner that, during a short transition period, the end portion of the yarn and the front portion (beginning) of the fiber strand move together through the twist generation means. Thereby, by means of the twist generation, the fibers of the fiber strand are tangled with the fibers of the yarn end portion and the front portion of the yarn fiber strand is connected in a kind of splicing action with the end portion of the yarn. Thereby, the spinning process is again put into operation.
With the starting of the spinning, i.e., with a restart of a spinning process, it is possible to proceed in the same way, whereby, in place of the end portion of the yarn produced before the spinning interruption, an auxiliary yarn is used.
In order that the piecing part allows a trouble free continuation of the spinning process, for this purpose, the piecing part and its periphery must comprise a sufficiently large tear resistance, i.e., this usually means, that this tear resistance should be at least as high as the tear resistance of the yarn being produced in the momentary spinning process.
Different methods are known to achieve a sufficient tear resistance of the piecing part. These methods act at the free yarn end portion, at the free point portion of the refined fiber strand and/or at the timed coordination of the movement of the yarn end portion and the fiber strand front portion by means of the twist generation.
From the publication DE-4240653-A1, it is, for example, well known to roughen the yarn end portion and/or remove fiber ends from the dense fiber strand of the yarn and to branch them off from the yarn, whereby the tangling procedure with the newly supplied fiber improves and the tear resistance of the piecing part is being increased.
From the same publication, it is also known to prepare the yarn end portion for splicing in such a manner, that the fiber mass gradually decreases towards the yarn end and that the yarn itself thus tapers towards the end. A yarn end portion tapered in such a manner is then led overlapping through the twist generation point for the splicing with a correspondingly tapered front portion of a longitudinal fiber structure (gradually increasing fiber mass).
The use of a “pointed” front portion of a fiber strand for the piecing is for example described in the publication of the U.S. Pat. No. 5,802,831 (Murata). According to this publication, a longitudinal fiber structure is drafted in a drafting unit before the twist generation, whereby the drafting unit comprises a pre-drafting zone at the inlet side and a main drafting zone at the outlet side. After an interruption of the spinning process the intake of the longitudinal fiber structure into the drafting unit and the pre-draft is stopped. In that the main draft is not stopped, the longitudinal fiber structure is torn between the pre-drafting zone and the main drafting zone and forms a free front portion there. After the interruption the intake and the pre-draft are again synchronized accordingly with the twist generation means, coupled to the corresponding drive unit and the yarn take-off. The front portion of the longitudinal fiber structure, which is assumed to have a tapered form caused by the tearing off action, is thereby first subjected to the main draft, whereby it is assumed that the tapering mentioned is stretched accordingly and thus presents an improved piecing part.
The method according to U.S. Pat. No. 5,802,831 is still refined according to the publications U.S. Pat. Nos. 5,809,764 and 5,934,058 (both Murata), in that the tapering front portion of the longitudinal fiber structure, before the stretching, is shortened by a short part by tearing off, and in that, in a draft of air, which is applied between the drafting unit and the twist generation point, the fiber mass of this front portion is additionally and accordingly reduced.
It does show that it is difficult to prepare piecing parts with the methods mentioned which will meet the requirements. The yarns pieced according to the methods mentioned tend to have a weak point with a too low fiber mass immediately after a piecing point. For this reason, an up to 200% increased fiber mass in relation to the remaining yarn is usually added to the piecing part, thus a safely sufficient tear resistance is given for the starting of the spinning.
The U.S. application, Publication No. US 2002/0144496, which corresponds to an older European application of the applicant (EP 01129189,5), is also concerned with this problem, and its content is taken as an integrating part of this application. The object of this older application is supplemented by the present invention.
Besides the piecing quality (strength of the piecing part), the state of the art of the piecing or the process for the starting of the spinning has still a further disadvantage. With these methods, the piecing procedure is not always successful, so that the ratio of failed piecing procedures in relation to the total number of piecing procedure attempts is relatively high.